Light-emitting material and organic electroluminescent device using the same

ABSTRACT

An organic electroluminescent device (OELD) is provided. The OELD includes a substrate, an anode, a cathode and an emissive layer. The anode and the cathode opposite to the anode are disposed over the substrate. The emissive layer is disposed between the anode and the cathode. The emissive layer includes a light-emitting material. The chemical structure of the light-emitting material represented by the formula [1]:  
                 
 
The chemically structure L is selected from a group consisting of the chemical structures AA, BB, AB, and the combination thereof. The chemical structure A of the formula [2]:  
                 
The chemical structure X is selected from the group 4A to 6A elements of the periodic table. 
 
The chemical structure B is aromatic hydrocarbons having n benzene, n is a integer of 1 to 8. The chemical structure B of the formula [3]:

This application claims the benefit of Taiwan application Serial No. 94112789, filed Apr. 21, 2005, the subject matter of which is incorporated herein by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates in general to a light-emitting material and an organic electroluminescent device using the same and, more particularly, to a light-emitting material including two pyrenes bonded together via different link rings and an organic electroluminescent device using the same.

2. Description of the Related Art

A conventional organic electroluminescent device (OELD) is a multi-layer stacked structure including a substrate, an anode, a cathode, a hole injection layer, a hole transport layer, an electron transport layer, an electron injection layer and an emissive layer. The anode, the hole injection layer, the hole transport layer, the emissive layer, the electron transport layer, the electron injection layer and the cathode are disposed on the substrate orderly from bottom to top. The emissive layer includes a host-dopant system, in which a few dopants are doped in host material. The way how to define the host-dopant system to be a fluorescent host-dopant system or a phosphorescent host-dopant system is illustrated as follows.

When a voltage is applied to the cathode and the anode, electrons are injected into the emissive layer from the cathode through the electron injection layer and the electron transport layer. Holes are injected into the emissive layer from the anode through the hole injection layer and the hole transport layer. After the electrons and the holes combine in the emissive layer, the host material is excited from a ground state to an excited state. Because the host material in the excited state is unstable, the host material certainly returns to the ground state and transfer energy to the dopants.

When the dopants receive the energy and are excited from the ground state to the excited state, singlet excitons and triplet excitons are generated by the dopants. In both the fluorescent dopants and the phosphorescent dopants, due to the distribution ratio of the electron spin state, the probability of forming the triplet excitons and the singlet excitons is approximately 3:1.

Electroluminescence occurs in the organic electroluminescent device while the singlet excitons or the triplet excitons return to the ground state by releasing photons. In the fluorescent host-dopant system, only the singlet excitons emit visible fluorescence when returning to the ground state. In the phosphorescent host-dopant system, when returning to the ground state, the triplet excitons emit visible phosphorescence and the singlet excitons emit light which can be transferred to phosphorescence through internal system crossing (ISC).

The conventional emissive layer includes pyrenes. The pyrenes are planar structures, easily resulting in π-π stacking among the pyrenes. As a result, the light color and the luminance efficiency of the organic electroluminescent device using pyrenes are affected seriously. Therefore, aryl group and t-butyl group are mostly induced in the conventional emissive materials, for acting as substituting group of pyrenes. Accordingly, the chemical structure of pyrenes having substituting group is three-dimensional, so as to decrease the effect of π-π stacking on the light color. Although the three-dimensional properties of pyrenes become better due to having the substituents, the substituting groups beside pyrenes lower the light color and the luminance efficiency of the organic electroluminescent device using pyrenes with the substituting group.

SUMMARY OF THE INVENTION

It is therefore an object of the present invention to provide a light-emitting material and an organic electroluminescent device using the same. The emissive layer including two pyrenes bonded together via different link rings can improve the three-dimensional properties of the light-emitting material. The limitations of the conventional design using pyrenes with substituting group to improve the three-dimensional properties of pyrenes can be avoided. Therefore, the present invention not only can decrease the effect of π-π stacking on the light color but also can avoid the decline of light color and the poor luminance efficiency in the conventional organic electroluminescent device using pyrenes with substituting groups. The light color and the luminance efficiency of the organic electroluminescent device using the light-emitting material of the present invention are much better than those of the conventional organic electroluminescent device including pyrenes with substituting groups. Moreover, the light-emitting material of the present invention has good thermal stability and luminance efficiency. The wavelength of the light emitted from the light-emitting material of the present invention inclines to that of blue light. As a result, the light-emitting material of the present invention is very suitable for blue light-emitting material or light-emitting material in another color.

The present invention achieves the above-identified objects by providing a light-emitting material. The chemical structure of the light-emitting material represented by the formula [1]:

The chemical structure L is selected from the chemical structures AA, BB, AB, and the combination thereof. The chemical structure “A” of the formula [2]:

The chemical structure X is selected from the group 4A to 6A elements of the periodic table.

The chemical structure B is aromatic hydrocarbons having n benzenes. N is an integer of 1 to 8. The chemical structure B of the formula [3]:

The present invention achieves the above-identified objects by providing an organic electroluminescent device including a substrate, an anode, a cathode, a hole transport layer, an electron transport layer and an emissive layer. The anode and the cathode opposite to the anode are disposed over the substrate. The hole transport layer is disposed between the anode and the cathode. The electron transport layer is disposed between the cathode and the hole transport layer. The emissive layer is disposed between the hole transport layer and the electron transport layer. The emissive layer includes a light-emitting material. Two pyrenes are bonded together via a chemical structure L to form the light-emitting material. The chemical structure of the light-emitting material represented by the formula [1]:

The chemical structure L is selected from the group consisting of the chemical structures AA, BB, AB and the combination thereof. The chemical structure A of the formula [2]:

The chemical structure X is selected from the group 4A to 6A elements of the periodic table.

The chemical structure B is aromatic hydrocarbons having n benzenes. N is an integer of 1 to 8. The chemical structure B of the formula [3]:

Other objects, features, and advantages of the present invention will become apparent from the following detailed description of the preferred but non-limiting embodiments. The following description is made with reference to the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates a cross-sectional view of an organic electroluminescent device according to the first embodiment using the light-emitting materials of the present invention;

FIG. 2 illustrates a flat panel display apparatus according to the second embodiment using the organic electroluminescent device of the present invention; and

FIG. 3 illustrates a flat panel display apparatus according to the third embodiment using the organic electroluminescent device of the present invention.

DETAILED DESCRIPTION OF THE INVENTION First Embodiment

A light-emitting material is provided in the present embodiment of the invention. Two pyrenes are bonded together via a different link ring L to form the light-emitting material, for improving the three-dimensional properties of the pyrenes. This design is totally different from the conventional design using pyrenes doped with substituting groups to improve the three-dimensional properties of the pyrenes. The main chemical structure of the light-emitting material of the present embodiment of the invention represented by the formula [1]:

The chemical structure L defines as the structure of the link ring for bonding the two pyrenes. The chemical structure L includes the chemical structure A and the chemical structure B. The chemical structure L can be selected from the group consisting of the chemical structures AA, BB, AB, and the combination thereof. The chemical structures A and B are illustrated in detail as follows. As to the definition of the chemical structure A, the chemical structure A of the formula [2]:

The chemical structure X is selected from the group 4A to 6A elements of the periodic table.

As to the definition of the chemical structure B, the chemical structure B is aromatic hydrocarbons having n benzenes. N is an integer of 1 to 8. The chemical structure B of the formula [3]:

In the present embodiment of the invention, the chemical structure X can be comprises carbon, oxygen, sulfur, nitrogen, or selenium. The chemical structure X can further includes a first substituting group. And the chemical structure X can still further includes a second substituting group. The first substituting group is selected from the group consisting of alkyl, alkoxy, alkylsilyl, aryl, heteroaryl, aryloxy, arylamino, arylsilyl, hydrogen, and any other substituting groups. The second substituting group is selected from the group consisting of alkyl, alkoxy, alkylsilyl, aryl, aryloxy, arylamino, arylsilyl, heteroaryl, hydrogen, and any other substituting groups.

Furthermore, the chemical structure X can include the first substituting group and the second substituting group. And the chemical structure B can further include a third substituting group. The first substituting group and the second substituting group are independently selected from the group consisting of alkyl, alkoxy, alkylsilyl, aryl, heteroaryl, aryloxy, arylamino, arylsilyl, hydrogen, and any other substituents. The third substituting group is selected from the group consisting of alkyl, alkoxy, alkylsilyl, aryl, aryloxy, arylamino, arylsilyl, heteroaryl, hydrogen, and any other substituting groups.

When the chemical structure X is carbon, the chemical structure A of the formula [IV]:

When the chemical structure X is nitrogen, the chemical structure A of the formula [V]:

The chemical structure B is selected from the group consisting of benzene, naphthalene, anthracene, phenanthrene, and biphenyl. The formulas of benzene, naphthalene, anthracene, phenanthrene and biphenyl are illustrated as follows:

As to the chemical structure of the chemical structure L is illustrated as modes AA, AB, BB, and the combination thereof. First, when the chemical structure L is mode AA, the formula is shown as follows:

Moreover, when the chemical structure L is mode BB, the formula is shown as follows:

Furthermore, when the chemical structure L is mode AB, the formula is shown as follows:

In the present embodiment of the invention, the light-emitting material formed by two pyrenes bonded together via the chemical structure L can be selected from the group consisting Dipyrenes fluorenyl anthracene (DPFA), Dipyrenes carbazoly anthracene (DPCA), Dipyrenes phenyl benzene (DPPB) and the combination thereof. The formulas thereof are shown as follows:

In DPFA and DPCA, the chemical structure L is mode AB described above. In DPPB, the chemical structure L is the mode BB described above.

The manufacture of DPFA is illustrated first as an example of the manufacture of the light-emitting materials revealed in the present embodiment of the invention.

In the process of manufacturing DPFA, first, in step (a), 9-(9,9-Diethyl-9H-fluoren-2-yl)-anthracene shown as a compound 3 is synthesized. The synthesizing equation is shown as follows:

In step (a), first, about 1.9 g (8.5 mmol) compound 1, about 2 g (7.5 mmol) compound 2, about 260 mg (0.23 mmol) Tetrakis(triphenylphosphine)palladium[Pd(PPh₃)₄,], and about 2 M, 7.5 ml K₂CO₃ solution (7.5 mmol K₂CO₃) are added into a bottle containing 20 ml ethanol (EtOH) and 10 ml Dimethoxyethane (DME). The volume ratio of EtOH and DME is about 2:1. The mixed solution is stirred and heated. Next, entire reactants boil and react until the other day. Afterwards, the compound 1 is traced by thin layer chromatography (TLC) to confirm whether the entire compound 1 reacts completely. Then, products of the pre-mentioned synthesizing formula remain in high temperature, and impurities of the products are filtered out by a glass filtering plate. Lastly, the filtered solution is re-crystallized in ethanol to obtain the compound 3 in high purity. The compound 3 obtained in step (a) weights about 3 g and its weight percentage is about 60%. The purity of the compound 3 is respectably high.

After the compound 3 is synthesized, (9-Bromo-10-(7-bromo-9,9-diethyl-9H-fluoren-2-yl)-anthracene shown as a compound 4 is synthesized in step (b). The synthesizing equation is shown as follows:

In step (b), in the condition of ice-bath, about 1.9 g (10.5 mmol) N-bromosuccinimide (NBS) is added into a bottle containing about 2 g (5 mmol) compound 3 and 10 ml Dimethylformamide (DMF). Reactants remain in room temperature (r.t.) and react until the other day. Then, on the other day, 40 ml saturated Na₂S₂O₄ solution is added. And 40 ml ethyl acetate is added for extraction. Afterwards, the mixed solution is dried out through condensing at reducing pressure. Next, the deposition is cleaned by deionized water (DIW) and n-hexane, as to obtain the compound 4 in high purity. The compound 4 obtained in step (b) weights about 1.9 g and its weight percentage is about 70%. The purity of the compound 4 is respectably high.

Finally, DPFA is synthesized in step (c). The synthesizing equation is shown as follows.

In step (c), first, about 1.9 g (3.4 mmol) compound 4, about 1.7 g (6.8 mmol) compound 5, about 231 mg (0.2 mmol) Pd(PPh₃)₄ and 2M, 6.8 ml K₂CO₃ solution (13.6 mmol K₂CO₃) are added in a bottle containing about 20 ml EtOH and about 10 ml DME. The volume ratio of EtOH and DME is about 2:1. The mixed solution is stirred and heated. Next, reactants boil and react until the other day. Afterwards, the compound 4 is traced by TLC to confirm whether the entire compound 4 reacts completely. Due to the poor solubility of product, the products can not be re-crystallized in EtOH. Therefore, after cleaned by DIW, the deposition is directly purified through sublimation to obtain the compound DPFA. The obtained compound DPFA weights about 814 mg, and its weight percentage is about 30%.

As to the manufacture and the synthesizing process of DPCA are described as follows:

In the process of manufacturing DPCA, first, a compound 6 is synthesized. Then, a compound 7 is synthesized. Lastly, DPCA is synthesized.

In the process of synthesizing the compound 6, the compound 1, a compound 9, Pd(PPh₃)₄ and K₂CO₃ solution are added in a bottle containing EtOH and DME. The volume ratio of EtOH and DME is about 2:1. The mixed solution is stirred and heated. Then, reactants boil and react until the other day. Afterwards, the compound 1 is traced by TLC to confirm whether the entire compound 1 reacts completely. Next, products of the pre-mentioned synthesizing formula remain in high temperature and are filtered by a glass filtering plate to filter out impurities. Lastly, the filtered solution re-crystallizes in EtOH to obtain the compound 6 in high purity.

In the process of synthesizing the compound 7, first, in the condition of ice-bath, NBS is added in a bottle containing the compound 6 and DMF. Next, reactants react in room temperature (r.t.) until the other day. Then, on the other day, saturated Na₂S₂O₄ solution is added. And ethyl acetate is added for extracting. Afterwards, solvent is dried out through condensing at decreasing pressure. Next, the deposition is cleaned by DIW and n-hexane to obtain the compound 7 in high purity.

In the process of synthesizing the compound DPCA, first, the compound 7, the compound 5, Pd(PPh₃)₄ and K₂CO₃ solution are added in a bottle containing EtOH and DME. The volume ratio of EtOH and DME is about 2:1. The mixed solution is stirred and heated. Next, reactants boil and react until the other day. Afterwards, the compound 7 is traced by TLC to confirm that the entire compound 7 reacts completely. Products in the pre-mentioned formula can not be re-crystallized in EtOH due to poor solubility. Therefore, the deposition is cleaned by DIW and then directly purified through sublimation to obtain the compound DPCA.

The manufacture and synthesizing process of DPPB are illustrated as follows:

In the process of synthesizing DPPB, first, compound 8, the compound 5, Pd(PPh₃)₄ and K₂CO₃ solution are added in a bottle containing EtOH and DME. The volume ratio of EtOH and DME is about 2:1. The mixed solution is stirred and heated. Next, reactants boil and react until the other day. Then, the compound 8 is traced by TLC to confirm that the entire compound 8 reacts completely. Products of the pre-mentioned formula can not be re-crystallized in EtOH due to poor solubility. Therefore, the deposition is cleaned by DIW and then directly purified through sublimation to obtain the compound DPPB.

Referring to FIG. 1, a cross-sectional view of an organic electroluminescent device according to the first embodiment using the light-emitting materials of the present invention is illustrated. The electroluminescent device can be organic light emitting diode (OLED) or polymer light emitting diode (PLED). In the present embodiment of the invention, OLED is illustrated as an example. However, the skill revealed in the present embodiment of the invention can be applied to PLED as well.

In FIG. 1, the electroluminescent device 10 includes at least a substrate 11, an anode 12, a cathode 13, an emissive layer 14, a hole transport layer 15 and an electron transport layer 16. The anode 12 and the cathode 13 opposite to the anode 12 are disposed over the substrate 11. The hole transport layer 15 is disposed between the anode 12 and the cathode 13. The electron transport layer 16 is disposed between the cathode 13 and the hole transport layer 15. The emissive layer 14 is disposed between the hole transport layer 15 and the electron transport layer 16 and includes the pre-mentioned light-emitting materials, such as DPFA, DPCA, DPPB and the combination thereof. Moreover, the organic electroluminescent device 10 further includes a hole injection layer 17 and an electron injection layer 18. The hole injection layer 17 is disposed between the hole transport layer 15 and the anode 12. The electron injection layer 18 is disposed between the electron transport layer 16 and the cathode 13.

When the light-emitting materials of the present embodiment of the invention act as host material, dopants can be doped in the emissive layer of the present embodiment of the invention to form a host-dopant system. The electroluminescent device, such as a fluorescent electroluminescent device or a phosphorescent device, can be built. When the light-emitting materials of the present embodiment of the invention act as dopants, the light-emitting materials of the present embodiment of the invention can be doped in host material in the emissive layer to form a host-dopant system as well. The electroluminescent device, such as a phosphorescent device or a fluorescent device, can be built. Therefore, the light-emitting materials revealed in the present embodiment of the invention can be applied widely and not limited to the above field.

However, anyone who has ordinary skill in the field of the present embodiment of the invention can understand that the invention is not limited thereto. For example, the anode 12 and the cathode 13 can be metal, alloy or transparent electrically conductive material. And one of the anode 12 and the cathode 13 is a transparent electrode or a translucent electrode. The pre-mentioned transparent electrically conductive material can be indium tin oxide (ITO), indium zinc oxide (IZO), cadmium tin oxide (CTO), stannim dioxide (SnO₂) zinc oxide (ZnO) or other similar transparent metal oxide. The pre-mentioned metal and alloy can include aurum (Au), aluminum (Al), indium (In), magnesium (Mg) and calcium (Ca).

When only the anode 12 is transparent or translucent, the cathode 13 can be a reflective metal. Then the organic electroluminescent device 10 is a bottom emission device. And the substrate 11 must be a transparent or a translucent substrate. When only the cathode 13 is transparent or translucent, the anode 12 can be a reflective metal. Then the organic electroluminescent device 10 is a top emission device. And the substrate 11 can be a transparent, a translucent or an opaque substrate. When both the anode 12 and the cathode 13 are transparent or translucent, the electroluminescent device 10 is a dual emission device. And the substrate 11 must be a transparent or a translucent substrate.

In the present embodiment of the invention, manufacturing method of the organic electroluminescent device 10 includes following steps. First, the substrate 11 is provided. Then, the anode 12 is formed on the substrate 11. Afterwards, the hole injection layer 17 is formed on the anode 12. Next, the hole transport layer 15 is formed on the hole injection layer 17. Then, the emission layer 14 is formed on the hole transport layer 15. The emissive layer 14 includes the pre-mentioned light-emitting materials, such as DPFA, DPCA, DPPB and the combination thereof. Next, the electron transport layer 16 is formed on the emissive layer 14. Subsequently, the electron injection layer 18 is formed on the electron transport layer 16. Afterwards, the cathode 13 is form on the electron injection layer 18. Therefore, the organic electroluminescent device 10 is completed.

Second EReferring to FIG. 2, a flat panel display apparatus according to the second embodiment using the organic electroluminescent device of the present invention is illustrated. A flat panel display apparatus can be a flat panel display 70, such as a computer screen, a flat panel television or a monitor screen. In the present embodiment of the invention, the flat panel display 70 is a computer screen for example.

In FIG. 2, the flat panel display apparatus 70 includes a housing 71 and a display panel 72. The display panel 72 at least includes the pre-mentioned organic electroluminescent device 10 and is disposed on the housing 71. Moreover, a display area of the display panel 72 is exposed to the surroundings through a front opening 71 a of the housing 71.

Third Embodiment

Referring to FIG. 3, a flat panel display apparatus according to the third embodiment using the organic electroluminescent device of the present invention is illustrated. A flat panel display apparatus can be a portable display apparatus 80, such as a mobile phone, a hand-held video game, a digital camera (DC), a digital video (DV), a digital displayer, a personal digital assistant (PDA), a notebook, or a table PC. In the present embodiment of the invention, the portable display apparatus 80 is a mobile phone for example.

In FIG. 3, the portable display apparatus 80 includes a housing 81, a display panel 82 and a set of press buttons 83. The display panel 82 at least includes the pre-mentioned organic electroluminescent device 10 and is disposed on the housing 81. Moreover, a display area of the display panel 82 is exposed to the surroundings through a front opening 81 a of the housing 81. The set of press buttons 83 is disposed on a front surface of the housing 81 and is positioned on a side of the display panel 82.

Furthermore, the organic electroluminescent device 10 of the present embodiment of the invention can be applied to any electric apparatus with a display panel.

Two pyrenes are bonded together via a different bond in the light-emitting materials and the organic electroluminescent devices using the same described in the embodiments of the present invention. The three-dimensional properties of the materials can be improved. And the limitations of the conventional design using pyrenes with substituents to strength the three-dimensional properties of pyrenes can be avoided. Therefore, the embodiments of the present invention can lower the effect of light color due to π-π stacking. Furthermore, the decline of light color and poor luminance efficiency in the conventional organic electroluminescent device using pyrenes with substituents can be avoided. The light color and the luminance efficiency of the electroluminescent device using the light-emitting materials of the embodiments of the present invention are much better than those of the conventional organic electroluminescent device using pyrenes with substituents. Moreover, the light-emitting materials synthesized in the embodiments of the present invention have good thermal stability and luminance efficiency. The wavelength of the light emitted thereof inclines to the wavelength of the blue light. Therefore, the light-emitting materials synthesized in the embodiments of the present invention are very suitable for blue light-emitting materials. Certainly, different colors of light with different wavelengths can be produced by different formulas. Therefore, the light-emitting materials of the present invention are very suitable for light-emitting materials in other colors as well.

While the present invention has been described by way of example and in terms of embodiments, it is to be understood that the present invention is not limited thereto. On the contrary, it is intended to cover various modifications and similar arrangements and procedures, and the scope of the appended claims therefore should be accorded the broadest interpretation so as to encompass all such modifications and similar arrangements and procedures. 

1. A light-emitting material represented by the formula [1]:

wherein the chemical structure L is selected from the group consisting of chemical structures AA, BB, AB, and the combination thereof, the chemical structure A of the formula [2]:

wherein the chemical structure X is selected from the group 4A to 6A elements of the periodic table; wherein the chemical structure B is aromatic hydrocarbons having n benzene, n is an integer of 1 to 8, and the chemical structure B of the formula [3]:


2. The light-emitting material of claim 1, wherein the chemical structure X further comprises a first substituting group selected from the group consisting of alkyl, alkoxy, alkylsilyl, aryl, heteroaryl, aryloxy, arylamino, arylsilyl, and hydrogen.
 3. The light-emitting material of claim 2, wherein the chemical structure X comprises carbon, oxygen, sulfur, nitrogen, or selenium.
 4. The light-emitting material of claim 3, wherein the chemical structure B is selected from the group consisting of benzene, naphthalene, anthracene, phenanthrene, and biphenyl.
 5. The light-emitting material of claim 1, wherein the chemical structure B further comprises a second substituting group selected from the group consisting of alkyl, alkoxy, alkylsilyl, aryl, aryloxy, arylamino, arylsilyl, heteroaryl, and hydrogen.
 6. The light-emitting material of claim 1, wherein the chemical structure X further comprises a first substituting group and a second substituting group selected from the group consisting of alkyl, alkoxy, alkylsilyl, aryl, aryloxy, arylamino, arylsilyl, heteroaryl, and hydrogen.
 7. The light-emitting material of claim 6, wherein the chemical structure X comprises carbon, oxygen, sulfur, nitrogen, or selenium.
 8. The light-emitting material of claim 7, wherein the chemical structure B is selected from the group consisting of benzene, naphthalene, anthracene, phenanthrene, and biphenyl.
 9. The light-emitting material of claim 8, wherein the chemical structure B further comprises a third substituting group selected from the group consisting of alkyl, alkoxy, alkylsilyl, aryl, aryloxy, arylamino, arylsilyl, heteroaryl, and hydrogen.
 10. An organic electroluminescent device (OELD), comprising: a substrate; an anode and a cathode opposite to the anode, disposed over the substrate; a hole transport layer disposed between the anode and the cathode; an electron transport layer disposed between the cathode and the hole transport layer; and an emissive layer, disposed between the hole transport layer and the electron transport layer, comprising a light-emitting material, the chemical structure of the light-emitting material represented by the formula [1]:

wherein the chemical structure L is selected from the group consisting of chemical structures AA, BB, AB, and the combination thereof, and the chemical structure A of the formula [2]:

wherein the chemical structure X is selected from the group 4A to 6A elements of the periodic table; wherein the chemical structure B is aromatic hydrocarbons having n benzene, n is an integer of 1 to 8, and the chemical structure B of the formula [3]:


11. The OELD of claim 10, wherein the chemical structure X further comprises a first substituting group selected from the group consisting of alkyl, alkoxy, alkylsilyl, aryl, heteroaryl, aryloxy, arylamino, arylsilyl, and hydrogen.
 12. The OELD of claim 11, wherein the chemical structure X comprises carbon, oxygen, sulfur, nitrogen, or selenium.
 13. The OELD of claim 12, wherein the chemical structure B is selected from the group consisting of benzene, naphthalene, anthracene, phenanthrene, and biphenyl.
 14. The OELD of claim 13, wherein the chemical structure B further comprises a second substituting group selected from alkyl, alkoxy, alkylsilyl, aryl, aryloxy, arylamino, arylsilyl, heteroaryl, and hydrogen.
 15. The OELD of claim 10, wherein the chemical structure X further comprises a first substituting group and a second substituting group selected from the group consisting of alkyl, alkoxy, alkylsilyl, aryl, aryloxy, arylamino, arylsilyl, heteroaryl, and hydrogen.
 16. The OELD of claim 15, wherein the chemical structure X comprises carbon, oxygen, sulfur, nitrogen, or selenium.
 17. The OELD of claim 15, wherein the chemical structure B is selected from the group consisting of benzene, naphthalene, anthracene, phenanthrene, and biphenyl.
 18. The OELD of claim 17, wherein the chemical structure B further comprises a third substituting group selected from the group consisting of alkyl, alkoxy, alkylsilyl, aryl, aryloxy, arylamino, arylsilyl, heteroaryl, and hydrogen.
 19. The OELD of claim 11 further comprising: an electron injection layer disposed between the cathode and the electron transport layer; and a hole injection layer disposed between the anode and the hole transport layer.
 20. A flat panel display apparatus, comprising the electroluminescent device of claim
 10. 